Ceilometer-api is crashing due to pecan module missing

Moving pecan module listing from test-requires
and test-requires-folsom to pip-requires so that
it can be used by both setup.py and tox.ini

Bug #1102614

Change-Id: I67cd45c068305ec7897d67b425b06173e092b9f8
Factorize agent code

There was some code duplication between the central and compute agent around
their managers, so let's factorize that.

Change-Id: I90514e7591833254145ceab366ad5a0d03d8f228
Signed-off-by: Julien Danjou <julien@danjou.info>
Merge "Ceilometer-api is crashing due to pecan module missing"